问题
多项选择题
理想垫底材料的条件（）
A.对牙髓没有刺激
B.不隔绝物理刺激
C.足够的抗压强度
D.不影响材料性能
E.临床的使用方便
答案
参考答案：A, C, D, E
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理想垫底材料的条件（）
A.对牙髓没有刺激
B.不隔绝物理刺激
C.足够的抗压强度
D.不影响材料性能
E.临床的使用方便
参考答案：A, C, D, E
以下是EMPLOYEE表的详细定义，其中也包括了约束的描述。
| EMPLOYEE | ||||||||
| Column Name | EMPLOYEE_ID | NAME | JOB | MANAGER | DATE_HIRED | SALARY | BONUS | DEPIARTMENT_ID |
| Key-Type | PK | |||||||
| Nulls/Unique | NN，U | NN | NN | |||||
| FK Table | ||||||||
| FK Column | ||||||||
| Datatype | HUM | VARCHAR2 | VARCHAR2 | NUM | DATE | NUM | HUM | NUM |
| Length | 6 | 20 | 9 | 6 | 7, 2 | 7, 2 | 2 | |
A．CREATE VIEW department_v
AS SELECT DISTINCT department
FROM
employee;
B．CREATE VIEW emp_info_v
AS SELECT employee_id, name, job, manager
FROM
employee;
C．CREATE VIEW emp_info_v
AS SELECT employee_id, name, job, manager, department_id, date_hired
FROM
employee;
D．CREATE VIEW dept_salary_v
AS SELECT department_id，AVG (salary) "average salary"
FROM
employee
GROUP BY department_id;